The topic title is a little vague, couldn't come up with a better one. Sorry for that.

I've searched the forums and tried several options for the last couple of days and I haven't found a solution I want so far and I was hoping you guys could help me with the following:

When I cold boot my laptop (Windows 8 x64) and I wake my NAS, everything is fine. I copy my files from and to my NAS with a transfer speed of around 39 MB/s. I have a Synology DS213j. I know this NAS could do quicker, but my laptop is the bottleneck in this one. No worries, 39 MB/s is fast enough for me. But if my laptop is on for a couple of hours and I've copied several files from and to my NAS, the performance drops to around 5~6 MB/s and there is no way to get the previous 39 MB/s back, until I reboot Windows.

I tried the following:

* Router reset.

* NAS restart.

* Against better knowledge: replaced my UTP-cables.

* Updated my network card drivers.

* Changed several settings on my NAS, like enabling / disabling SMB2 and Large MTU support.

* Changed the setting of my network card to force it to "full duplex / 1gbps" instead of "auto negotiation".

All to no avail. It only helps to reboot Windows. After the Windows reboot my network speeds is up to 39 MB/s again. It's like smb/cifs is "full" or just bogged down. This doesn't happen if I use my MacBook which uses AFP.

So I was thinking: is there a way to reset the network within Windows instead of doing a complete reboot? Like enabling / disabling a service using a script or some sort? Or if you know a solution to this problem, I'm all ears.

I meant smb/cifs cache is full/to many connections "left" open or something, I'm just guessing here. Find it rather strange my networkspeed just drops down like that. And no, the established connection stays at 1.0 gbps, according to Windows.

I was thinking the same thing, after a while the computer puts the NIC in hibernation and when it comes back it "auto negotiates" at 100mbps instead of 1.0 gbps. But that's not the case, at least according to Windows Networkcenter.

I have no thorough knowledge of the SMB/cifs protocol, so I'm guessing as to why this happens. Good to know it can't be that.

I know gigabit should be set to auto, I tried forcing it as a gigabit connection just for testing purposes, but to no avail. It's back to auto now.

And no, I've thought of that, but I physically disabled my wireless adapter. (Touch sensitive switch on the laptop itself). Just to be sure, I also removed my own network from prefered networks within Windows. So even if the wireless card does power on somehow it won't be able to connect to my network.

Thank you +BudMan! Tonight, when I get home from work, I'll do a robocopy of a random generated (using /dev/urandom) 700mb file when I get home (so the speed is ok) and after a couple of hours and when it happens again, I'll do a robocopy of the same file and post the results.

* Powered on my laptop and copied a (somewhat) 600 MB file to my NAS. Results are in the first screenshot.

* Left my laptop powered on and came back roughly 1 hour and 45 minutes later. Removed the file from my NAS and exeuted the exact same robocopy command using the up-arrow key in CMD. Results are in the second screenshot.

* Screenshot 3 shows my network speed after both tests, still at 1.0gbps, but as you can see, my speed dropped drastically. To get the full speed back I had to reboot my laptop. Before I did that, I reset my router, restarted my NAS, all to no avail. Reboot Windows and voila, I'm back on my initial transfer speed from screenshot 1.

It's an Acer Aspire 6930G (734G32Bn). Latest official BIOS version: 3238. The NIC in this laptop is broken, so I'm using an USB NIC from Sitecom. It's an Sitecom LN-032 (USB to Gigabit LAN), which is just a rebrand of an ASIX AX88179 controller. I've tried Sitecom's drivers v1.001 (the only driver for WIndows 8, which is based on the ASIX 1.16.5.0 driver) and the latest general ASIX 1.16.9.0 driver. Both drivers produce the same result.

The laptop is set to "High Performance" in Windows with all sleep / hibernate options disabled.

The USB Nic throws a whole new light on this issue in my mind, now its not simply how windows controls the Nic (via driver) but we now have USB bus thrown into the mix and how power management is handling USB.